Crossbar connections are common in large integrated circuits (ICs). On such ICs, a crossbar connection provides connections between multiple requesting units and multiple resources. Such requesting units may comprise processors or input channels. The resources may comprise interleaved components of a large memory or output channels. A conductive pathway (e.g., a wire) exists from each requesting unit to each resource. In some systems, each resource is potentially accessible by multiple requesting units. To accommodate such shared use of a resource, arbitration logic is provided for each resource. Thus, each requesting unit has conductive pathways to each such arbitration logic.
For a system comprising, for example, 10 requesting units and 10 resources (and commensurate arbitration logic units), each requesting unit has 10 conductive pathways to each of the 10 resources for a total of 100 conductive pathways from requesting units to resources. Another 100 conductive pathways may be provided as well for return messaging back to the requesting units; that is, 200 conductive pathways total. The number of conductive pathways increases non-linearly with the number of requesting units and resources available to such units. For example, for 256 requesting units and 256 resources/arbitration logic units, the number of conductive pathways exceeds 131,000.
The sheer volume of conductive pathways/wires on an IC can become hugely problematic for the design and construction of the IC. The space required for the conductive pathways may be larger than the real estate required for the functional circuitry itself.